Physics Midterm Two
Which conversion factor pair will convert meters per second to kilograms per hour?
(1km/1000m)(3600s/1hr)
A 1000kg crate is sliding along rollers across the factory floor with a total mechanical energy of 20,000 J. If the crate eventually comes to a complete stop on a level ground in 100m, what amount of force was applied by a factory employee pushing against the crate?
-200 N
A male figure skater has a mass of 80 kg and his lady partner has a mass of 55 kg. They spin around like crazy people and then the man launches the lady into the air away from him for 0.5 seconds changing her velocity 2.5 m/s. The ice has basically no friction. What is the force the man experiences?
-275N
Two billiard balls having the same mass and speed roll toward each other. What is their combined momentum after they meet?
0
In a physics lab, a 0.500 kg cart moving at 36.4 cm/s collides inelastically with a second cart which is initially at rest. The two carts move together with a speed of 21.8 cm/s after the collision. Determine the mass of the second cart.
0.500kg*36.4cm/s = momentum = 18.2. 18.2/21.8 = 0.83kg
How many grams are in a kilogram?
1000
A football player kicks a ball with a force of 100N. Find the impulse on the ball if his foot stays in contact with the football for 0.03s.
100N * 0.03s = 3Ns
It takes 40J to push a large box 4 m across the floor. Assuming the push is in the same direction as the move, what is the magnitude of the force on the box?
10N
Calculate the momentum for a 9 kg ball that accelerates for 1.5 m/s^2 for 5 seconds
13.5N = 9kg X 1.5 m/s^2. 13.5NX5=67.5kg*m/s^2
A ball is moving at 3 m/s and has a momentum of 48 kg m/s. What is the balls mass?
16 kg
A 1-kg chunk of putty moving at 1 m/s collides with and sticks to a 5-kg bowling ball initially at rest. The bowling ball and putty then move with a momentum of
1kg m/s
A rifle of mass 2 kg is suspended by strings. The rifle fires a bullet of mass 0.01 kg at a speed of 200 m/s. The recoil velocity of the rifle is about
1m/s
A male figure skater has a mass of 80 kg and his lady partner has a mass of 55 kg. They spin around like crazy people and then the man launches the lady into the air away from him for 0.5 seconds changing her velocity 2.5 m/s. The ice has basically no friction.What is the acceleration of each?
2.5/0.5 = 5m/s. lady friend = 5 m/s
Calculate the momentum of a 2000 kg car traveling at 15 m/s.
2000kg * 15m/s = 30,000 kg.m/s
A 4 kg ball has a momentum of 12 kg m/s. What is the ball's speed?
3 m/s
What is the system momentum after the collision?
30 kg m/s
What is the system momentum before the collision?
30 kg m/s
A TV set is pushed a distance of 2m with a force of 20N. How much work is done on the set?
40 J
A 20 N force is applied to move a 20 kg object a horizontal distance of 20 m at a constant speed. How much work was done?
400 J
Using 1000 J of work, a toy elevator is raised from the ground floor to the second floor in 20 seconds. The power needed to do this job was...
50 W
A diver who weighs 500 N steps off a diving board that is 10 m above the water. The diver hits the water with kinetic energy of...
5000J
Calculate the velocity of a 1.33 kg ball with a momentum of 5 kg m/s.
5kg.m/s * 1.33kg = 3.75 m/s
A 5000-kg freight car runs into a 10,000-kg freight car at rest. They couple upon collision and move with a speed of 2 m/s. What was the initial speed of the 5000-kg car?
6 m/s
The force constant of a spring is 125.0 N/m. How much force is required to stretch the spring 0.50 m?
62.5N
A 100 N force is applied to the same object from above at 45 degrees from the horizontal to move the object 15 m. How much work was done?
67500 J
The world record for pole vaulting is 6.15 m. If a pole vaulter's gravitational potential is 4942 J, what is his mass?
82kg
Which of the following has the largest momentum relative to the Earth's surface?
A pickup truck speeding along a highway
When you jump from an elevated position you usually bend your knees upon reaching the ground. By doing this, you make the time of the impact about 10 times as great as for a stiff-legged landing. In this way the average force your body experiences is
About 1/10 as great
On earth (but on every other planet or astronomical body) a feather and a coin dropped in a vacuum fall with equal...
Accelerations
You are driving a giant diesel engine truck down the highway. Unfortunately, a cute little butterfly collides with your windshield. Explain using words and equations how the force your truck feels is equal to the force the butterfly felt prior to becoming an ex-bug.
According to Newton's third law, every action force has an equal and opposite reaction. Although the butterflies mass is smaller than the truck's, the force experienced by both of them was the same.
Total mechanical energy can be found by...
Adding potential and kinetic energies together
A freight train rolls along a track with considerable momentum. If it rolls at the same speed but has twice as much mass, its momentum is
Doubled
A male figure skater has a mass of 80 kg and his lady partner has a mass of 55 kg. They spin around like crazy people and then the man launches the lady into the air away from him for 0.5 seconds changing her velocity 2.5 m/s. The ice has basically no friction. What is the force the lady experiences?
F=m*a. 55kg*5m/s = 275N
Two identical arrows, one with twice the speed of the other, are fired into a hay bale. the faster arrow will penetrate...
Four time further than the slower arrow
How do the three surfaces compare in terms of providing the egg with a safe landing? Which ordering below ranks the three surfaces from least safe to most safe?
Hard floor < 1-ince foam < foam box
Using physics, explain why having seat belts and air bags installed into all cars, trucks, etc. should be a "no brainer" for engineers and drivers.
If you're inside the car that's traveling at a certain momentum, you're momentum is the same as the car's. If the car crashes suddenly, without airbags and seat belts, the force suddenly placed upon you by deceleration would fling you forward into the windshield.
An open freight car rolls friction free along a horizontal track in a pouring rain that falls vertically, as water accumulates in the car, the car's speed...
Increases
When an object is in motion, which of the following could not have a value of zero?
Inertia
What is the standard unit for work?
Joule
Which mass unit is the "ideal" unit when working with momentum and impulse problems?
Kilograms
Which velocity unit is the "ideal" unit when working with momentum and impulse problems?
Meters per second
Two objects have the same size and shape, but one is much heavier than the other. When they are dropped simultaneously from a tower, they reach the ground at the same time, but the heavier one has a greater
Momentum
If a ping pong ball and a golf ball are both moving in the same direction with the same amount of kinetic energy, the speed of the ping pong ball must be...
More than the golf ball
If a monkey floating in outer space throws his hat away, the hat and the monkey will both
Move away from each other, but at different speeds
Momentum is transferred to the ground when an apple falls on it. The momentum absorbed by the ground is
Negligible compared to the momentum of the apple
The conservation of momentum is most closely related to
Newtons third law
If you push for a half hour or a whole hour against a stationary wall...
No work is done on the wall in either case
A 2-kg mass is held 4 m above the ground. What is the approximate potential energy of the mass with the respect to the ground?
PEgrav = m . g . h/ 9.81 . 2 . 4 = 78.48. 80J
A job is done slowly, while an identical job is done quickly. Both jobs require the same amount of work, but different amounts of...
Power
What is the standard unit for time?
Second
Which has a greater kinetic energy, a car traveling at 30 km/hr or a car of half the ass traveling at 60 km/hr?
The 60km/hr car
If an object is lifted from the ground to 3 meters by doing 1000 J of work, the total mechanical energy MUST equal
The GPE of the object plus 1000 J
A flower pot of mass m falls from rest to the ground below, a distance h. Which statement is correct?
The KE of the pot when it hits the ground is proportional to h
It is correct to say that impulse is equal to
The change in momentum it produces
Which statement describes the effect of increasing drop height upon the force encountered?
The force is directly related to the drop height
The force on an apple hitting the ground depends upon
The speed of the apple just before it hits
To catch a ball, a baseball player extends the hand forward before impact with the ball and then lets it ride backward in the direction of the ball's motion. Doing this reduces the force of impact on the player's hand principally because the
Time of impact is increased
Two identical arrows, one with twice the kinetic energy of the other, are fired into a hay bale. The faster arrow will penetrate...
Twice as far as the slower arrow
A 1000-kg car and a 2000-kg car are hoisted the same distance. Raising the more massive car requires...
Twice as much work
What is the standard unit for power?
Watt
Was momentum conserved?
Yes
If you push an object twice as far while applying the same force, you do
twice as much work
